A burr arises during the manufacturing of bevel gears, depending on the tool used and technology used, due to the chip producing machining on the outer tooth end.
Before the burr formation and the deburring are discussed, the corresponding environment is to be defined more precisely on the basis of several fundamental considerations and on the basis of drawings.
FIG. 1A shows a schematic side view of a bevel gear pinion 31, wherein elements and terms are defined based on this side view and as they are used in the present application. FIG. 1B shows the main body 60 of a bevel gear pinion 31 according to FIG. 1A in schematic form. The example shown relates to a bevel gear pinion 31 having curved flank longitudinal line. However, the invention may also be applied to other bevel gears 31. In the example shown, the bevel gear pinion 31 has a main body 60, which is defined by two truncated cones KK and FK having corresponding cone skin surfaces, as shown in FIG. 1B. These cone skin surfaces are, strictly speaking, truncated cone skin surfaces. The cone skin surfaces of the corresponding full cone provided with the reference signs 61 and 62 are referred to as the back cone surface and as the head cone surface. The intersection lines of the back cone surface with the plane of the drawing are shown by the auxiliary lines 61. The intersection lines of the head cone surface with the plane of the drawing are shown by the auxiliary lines 62. The two truncated cones KK and FK each have a cover surface 71 and 73, respectively, and a main surface 72 and 74, respectively, extending in parallel thereto. Both truncated cones KK and FK are arranged coaxially to the workpiece axis of rotation R1, wherein the main surface 72 of the truncated cone KK touches the main surface 74 of the truncated cone FK. The two truncated cones KK and FK are thus oriented opposite to one another in the example shown.
The teeth 75 of the bevel gear pinion 31 extend along the head truncated cone skin surface. The reference end face of the truncated cone 31 is identified with 63 and the rear end face is identified with 64. The end face 64 corresponds here to the cover surface 73 of the truncated cone FK. The truncated cone skin surface shown in gray in FIG. 1A, which represents a ring-shaped part of the rear cone surface, is referred to here in general as a (ring-shaped) heel-side skin surface 65. In the transition region from the teeth 75 to the heel-side skin surface 65, burrs 70 can arise during the chip producing machining (referred to here as gear cutting or gear chip producing machining) (see FIG. 3). These burrs form above all on the concave tooth flanks of the teeth 75 or in the transition region of the concave tooth flanks to the heel-side skin surface 65, respectively. This transition region is identified with P in FIG. 1A, wherein it is to be noted that the burrs 70 can occur both on the tooth flanks and on the tooth base. A burr 70 usually arises only on the heel (in the region P here), when milling is performed from the inside to the outside, i.e., when a tool coming through the tooth gap 67 exits from this tooth gap 67 in the region of the heel-side skin surface 65. In FIG. 1A, a block arrow is drawn in the tooth gap shown in the middle, which indicates the cutting direction of a tool during the exit from this tooth gap 67. In FIG. 1, the passage of a tooth gap 67 through the surface 65 in the region of the rear cone skin surface 65 is shown by dotted lines.
FIG. 2 shows details of a further bevel gear 31, wherein this image was derived from the standard DIN 3971, “Begriffe und Bestimmungsgröβen für Kegelräder und Kegelradpaare [terms and determinants for bevel gears and bevel gear pairs]”, July 1980. The terms of this DIN standard are used hereafter, as they are required and relevant. FIG. 2 shows an axial section. Auxiliary lines are shown in the region of the head truncated cone KK, which all intersect with the workpiece axis (of rotation) R1. Viewed from the outside to the inside, the following auxiliary lines 62, 63, and 66 are to be found in the region of the head cone, wherein the auxiliary lines 62 are intersection lines (dashed) of the head cone skin surface with the plane of the drawing, the auxiliary lines 63 are: intersection lines (dashed) of the index cone skin surface with the plane of the drawing, and the auxiliary lines 66 are intersection lines (solid lines) of the heel cone skin surface with the plane of the drawing.
The head cone tip is identified with KKs. In the example shown, the mentioned intersection lines 62, 63, and 66 do not extend in parallel to one another, but rather they are each defined by different cone angles. The base cone angle δf is of particular significance for the invention. This angle is therefore shown in FIG. 2. In the case shown, the tips of the head cone KKs, the index cone, and the base cone do not lie in the same point of the workpiece axis R1. Therefore, the tooth height h increases considered in the direction of the tooth width p (originating from the head cone tip KKs). The tooth height during the passage through the heel-side skin surface 65 is identified with he (see FIG. 2). In the case shown, the teeth are shorter at the small diameter of the bevel gear (called the toe) than at the large diameter (called the heel).
Auxiliary lines are also shown in the region of the heel cone in the example. These are the auxiliary lines 61 (dashed) of the heel cone skin surface with the plane of the drawing. These auxiliary lines 61 intersect with the workpiece axis R1 in the heel cone tip FKs. The cone angle δv of the heel cone is also of particular significance for the invention. This angle is therefore also shown in FIG. 2. Furthermore, the following angles are important: head cone angle δa and angle of the heel edge δ2.
The mentioned burrs primarily form in the region of the heel-side skin surface 65. A simplified and enlarged illustration of a bevel gear 31 is shown in FIG. 3, which only has a single tooth gap 67 here. The bevel gear 31 of FIG. 3 has a large base cone angle δf on the cone head (δf is approximately 80° here). The cone angle δv of the heel cone is approximately 10° here. The specifications and the corresponding drawings are solely of a schematic nature and are only to be understood as examples for better illustration.
The passage of the tooth gap 67 through the heel-side skin surface 65 approximately has a U-shape or V-shape here. A burr formation can occur in the region of the lateral legs of the U-shape (above all on the concave tooth flank, which is located on the right in the region of the tooth gap 67 here) and in the base region of the U-shape. The following relates in particular to the burr formation in the base region. A burr 70 (also referred to as a heel-side burr here) is indicated (shown shaded) in simplified form in FIG. 3, which extends in the base region and along the concave tooth flank. A block arrow is also shown here (as in FIG. 1A) in the tooth gap 67, which indicates the cutting direction of a tool, which is moved through the tooth gap 67 and leaves the tooth gap 67 in the region of the heel-side skin surface 65.
The present invention relates especially to the heel-side burrs 70 of bevel gears, since the burrs 70 are particularly complex and difficult to deburr.
It is considered to be a further disadvantage that special milling cutters may be used to remove heel-side burrs in bevel gears.
In the production of bevel gear pinions, the deburring is particularly problematic especially on the heel side of the bevel gear pinion, since the rear end face 64 of the bevel gear 31 is frequently accessible only partially or not at all in a conventional gear cutting machine, as can be inferred from schematic FIG. 4.
FIG. 4 shows a schematic sectional view of a bevel gear 31 having shaft 32. The shaft 32 is accommodated in a workpiece spindle 33. The heel-side skin surface 65 is only accessible with difficulty in the region X, since little space is present between the skin surface 65 and the workpiece spindle 33.
The deburring in the base region on the heel side is only possible with effort for the mentioned reasons.